Based on the field investigation of a large number of cases of seepage control and reinforcement of dangerous reservoir dams, combined with the introduction of literature, this paper sums up many factors that may affect the seepage control effect of the seepage control wall in the stage of survey, design and construction, and reasonably classifies the possible adverse effects. Based on the above classification, a simplified physical model was established, and seep/W module in GeoStudio was used to carry out seepage simulation, so as to evaluate the seepage control effect after the anti-seepage wall of earth rock dam was strengthened. Finally, taking the effect of seepage control and reinforcement of a reservoir as an example, the paper analyzed the existing quality defects, the difference of seepage control structure form, unstable seepage caused by water level change and other working conditions, evaluated the influence degree of each working condition factor on seepage control effect through the hydraulic gradient at the escape point, seepage flow and other factors, and carried out the preliminary judgment of the adverse causes of seepage control effect of seepage control body combining with the shape of seepage line, and does not The numerical simulation was carried out under the same reservoir water level and reservoir water level fluctuation conditions, and the difference of the phreatic line shape was compared and analyzed. The results show that the penetration defects seriously weaken the seepage control effect of the anti-seepage wall. Compared with the steady-state reservoir water level, the change of phreatic line under the different rate of sudden rise and fall of reservoir water level shows the phenomenon of "delayed rise"and "delayed fall" in the upstream. Through the above research, the seepage control of the dangerous reservoir is realized It can provide reference for reinforcement and renovation.